[Wien] negative epsilon 1

[Brik Hamida]

Hi
Im working on semiconductor material. I have calculated  the real part of
dielectric function (epsilon1) as function of energy. For high energy , I
found epsilon1 negative !
Please can someone explain me what means this negative values ? I read that
any material havig an negative epsilon1 , it becomes a metal , it is right
??
Thanks in advance
Brik
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